Ultra-processed foods are more likely to be abused

An entire bag of potato chips is around 1,200 calories — or 30 peaches. Why do we sometimes "slip up" and eat an entire bag of chips while binge-watching Netflix, but never "slip up" and eat 1,200 calories worth of peaches?

People are more likely to overeat and consequently gain weight when consuming ultra-processed foods, or "formulations mostly of cheap industrial sources of dietary energy and nutrients plus additives, using a series of processes", according to an experiment outlined in a recent study published in Cell Metabolism.

"Ultra-processed foods" is a fancy way of saying "junk food" — like chips, candy and soda.

The answer to the potato chips vs. peaches question may be obvious — potato chips taste better! According to the study, however, this logic doesn't add up. Scientists found that people's likelihood to overeat has little to do with taste.

Read more here: Ghana's obesity problem tied in with junk food

The experiment

Eating candy and chips has long been associated with adverse health effects, but scientists haven't demonstrated a causal relationship between the two in a controlled setting.

In an experiment conducted by researchers at the National Institutes of Health in the United States, 20 healthy adults resided at a research unit for four weeks and were randomly assigned to an ultra-processed or unprocessed diet for the first half of their stay, and the alternate for the second half. 

Unprocessed diets were made up of items such as grilled beef, barley and salads, while processed diets were made up of hamburgers, fries and macaroni and cheese. The meals were similar in calories, sugar and fat. Participants were allowed three meals a day, along with snacks, and were allowed to eat as much as they wanted during each meal. 

Researchers found that people on the ultra-processed diet consumed around 500 calories more than those on the unprocessed diet, and consequently gained an approximate kilogram of weight over the two week time span. Participants on the unprocessed diet lost an approximate kilogram of weight over the time span.

Although participants rated their unprocessed meals as being as filling and satisfying as their ultra-processed meals, they ate significantly more during their ultra-processed meals.

The study also described a higher "eating rate" among those on the ultra-processed diet — basically, they ate faster.

Past studies have outlined a link between the ingestion of soft, chewable foods (like white bread and macaroni and cheese) and delayed satiety signaling. To put it simply, you're more likely to feel full faster after eating 350 calories worth of grilled chicken with green beans than when you drink a 350-calorie milkshake.

Read more here: Can a junk-food tax save the Navajos? 

Caveats

Highly processed foods were first introduced in the Industrial Revolution because they served a purpose — they were cheap.

"Ultra-processed foods are less expensive and more convenient than preparing meals using unprocessed whole foods and culinary ingredients," the study said.

In the experiment, the weekly cost of ultra-processed groceries was around $150 for unprocessed meals and $100 for hyper-processed meals.

Although acknowledging the health effects of hyper-processed foods, the study acknowledged that it did not address how consumer choices between ultra-processed versus unprocessed meals may be influenced by cost and convenience.

Read more here: WHO: Curb ads for junk food, sweets and beer to fight obesity